Answer to Question #8936 Submitted to "Ask the Experts"

Category: Nuclear Medicine Patient Issues — Positron Emission Tomography (PET)

The following question was answered by an expert in the appropriate field:

Q

I work in a hospital and learned that after eight months of work, my employee bathroom is also used for PET (positron emission tomography) scan patients to empty their bladders and they have radioactive urine. How much exposure was this? Why doesn't the hospital have to put up a sign about the radiation? It really scares me.

A

It is difficult to say how much, if any, radiation exposure you have received over the eight months without actual survey data from the restroom.

However, it is likely you have received little exposure based on two things: (1) PET emitters are very short lived with the longest lived being about a two-hour half-life (meaning that after two hours, anything in the room with that radioactivity on it now has half the radioactivity on it and, after four hours, has only a quarter of the radioactivity on it) and (2) once flushed, essentially nothing remains unless the patient expelled some urine on the seat and you sit on the seat when you use the bathroom.

The real answer lies in whether there is radioactivity remaining on the seat after use by a patient, how much radioactivity is on the seat, and whether you sit on the seat and for how long and how many times. To get an answer to the first question, you can ask workers in the PET department if they have ever done surveys—if so, ask for their results and, if not, ask them if they could. They can then assist in interpreting that information for your exposure based on your usage habits.

Kelly Classic
Certified Medical Health Physicist

Ask the Experts is posting answers using only SI (the International System of Units) in accordance with international practice. To convert these to traditional units we have prepared a conversion table. You can also view a diagram to help put the radiation information presented in this question and answer in perspective. Explanations of radiation terms can be found here.
Answer posted on 19 March 2010. The information posted on this web page is intended as general reference information only. Specific facts and circumstances may affect the applicability of concepts, materials, and information described herein. The information provided is not a substitute for professional advice and should not be relied upon in the absence of such professional advice. To the best of our knowledge, answers are correct at the time they are posted. Be advised that over time, requirements could change, new data could be made available, and Internet links could change, affecting the correctness of the answers. Answers are the professional opinions of the expert responding to each question; they do not necessarily represent the position of the Health Physics Society.